One known type of plant for producing ethylene comprises a reactor into which oxygen and methane are introduced to effect oxidative coupling of methane. In this reaction methyl radicals are initially formed at high temperatures (about 600-880° C.) over a catalytic surface (e.g. two- or multicomponent metal oxide catalyst comprising alkali elements, alkaline earth elements and/or elements selected from the group of rare earths) in the reactor. The methyl radicals then recombine in the gas phase to form ethane which is converted into ethylene in the further course of the reaction. A first material stream comprising at least ethane and ethylene is obtained as a result. The plant further comprises a work-up unit fluidly connected to the reactor and configured to separate the first material stream into at least a C1− material stream and an ethylene product stream. The C1− material stream comprises hydrocarbons having one carbon atom and CO and H2. The plant further comprises a separator (e.g. pressure swing adsorber) connected to the work-up unit and configured to separate the C1− material stream into a hydrogen-rich hydrogen product stream and a hydrogen-lean residual gas stream which is typically fired. A method and apparatus for the catalytic conversion of methane to hydrocarbons having at least two carbon atoms is described in NL9300168.
Another existing method of ethylene or olefin preparation is steam cracking. This method comprises mixing a hydrocarbon-containing input with steam and typically passing the input gas thus formed through metallic tubes of a cracking furnace to effect cracking. The tubes are externally heated with burners to provide the necessary heat for the endothermic cracking process. The olefin-containing and hydrogen-containing crude gas stream thus obtained is typically purified and fractionated into the desired olefins, in particular ethylene.
There remains a need in the art for improvements to a plant and a process of ethylene production.